1. Technical Field
The present invention relates to a gripper or clamping device for manually operated or automatic handling devices, having a gripper housing, at least one base jaw displaceably seated in the gripper housing, and a drive for the base jaw, wherein the drive comprises a hydraulically or pneumatically chargeable piston displaceably seated in a cylinder and a spline hook gear.
2. Background Art
A gripper device of this type is known from DE 89 02 325 U1, for example. In order to be able to grip tools simply and yet precisely with a handling device or a robot arm, parallel grippers which are pneumatically or hydraulically actuated are employed as a rule. In the process a piston, which is displaceably seated in a cylinder provided in the gripper housing, is acted upon by a pressure medium. A spline hook gear is actuated by the displacement of the piston, so that the gripper jaws are extended out of the gripper housing or are retracted into the gripper housing. The base jaws have a T-shaped cross section and are seated in appropriate guides. The essential advantage of these base jaws, besides the relatively large gripping force, is the great lateral stability and small tendency for tilting. However, it has been found that the base jaws, and in particular their running surface, are subject to great wear, since the rinsing fluid which is sometimes used in the work area washes the lubricants off the guide surfaces because of the open guides, and furthermore, dirt particles penetrate between the housing and the base jaws. The dirt particles in particular cause a great amount of abrasion on the sliding surfaces, so that exact guidance and freedom from play is lost after a short time.
The present invention is therefore based on the object of further developing a gripper device of the type mentioned at the outset in such a way that wear is reduced, even when it is used in very dirty areas and also in case of contamination with rinsing liquids and similar fluids, and that the gripper device still moves easily even after longer use.
This object is attained in accordance with the present invention in that the base jaw has a sealed, for example circular or polygonal, cross section at least in the section extending from the gripper housing when the gripper device is opened.
The circularly shaped base jaws can be guided in a considerably more sealed manner in the housing, since the passages or receiving openings for the base jaws in the gripper housing can be manufactured considerably more precisely than a T-shaped opening for T-shaped base jaws. Neither foreign particles nor liquids can enter into the space between the housing and the base jaws because of the more precise fabrication of these receiving openings. The service life of such a gripper device is increased considerably over that of the known gripper devices in accordance with the prior art.
In connection with a preferred further embodiment it is provided that the housing is equipped with sealing elements enclosing the circular section of the base jaws. These sealing elements have the purpose of closely surrounding the base jaws and by means of this to prevent the possible further penetration of solid bodies or liquids or even gases. In addition, the sealing elements have the advantage that no lubricant emerges from the housing.
In order to protect the seals of the sealing elements, they can be advantageously provided with strippers, so that dirt and liquid adhering to the base jaws is stripped off. In this case the seals and strippers are advantageously combined into a single sealing element or are made of one piece. The latter is inserted into the housing in the area of the housing opening. The gripper in accordance with the present invention can now also be employed without problems in very dirty rooms where, for example, cast parts are dressed and abrasive cast dust accumulates.
In a further embodiment of the gripper device it is provided in accordance with the present invention that at least one of the base jaws is equipped with a protection against torsion. The lateral stability of the base jaws and therefore that of the gripper jaws is considerably increased by means of this protection against torsion, and the tendency to tilt is reduced. The workpieces can now be gripped and held by the gripper jaws which are secure against torsion.
It is provided in connection with a preferred embodiment that the protection against torsion has a groove provided in the base jaw, which is engaged by a feather key supported on the housing. In this case the groove for the feather key extends parallel with the longitudinal axis of the base jaw, wherein the groove is only provided in the section of the base jaw which remains in the housing. The section of the base jaw being extended out of the housing therefore has no groove, so that sealing is assured.
In order to be able, in a simple, but effective manner to compensate for tolerances, the feather key is floatingly seated in the housing, i.e. the feather key is fastened on a housing cover and is in particular made of one piece with it. In this way the insertion of the feather key into the grooves of the base jaws is possible without problems, even if the grooves in the base jaw are not exactly aligned with the housing opening receiving the feather key. The housing is open in the area of the groove, wherein this opening, however, is wider as well as longer than the feather key, and this housing opening can be closed by means of a cover which has the feather key. The feather key is inserted into the corresponding grooves when the cover is placed on the housing and the housing is closed, and as a result the base jaws are secured against torsion. Therefore the entirety of the forces acting on the feather key are supported by means of the cover of the housing. Large forces can be transmitted because of the relatively wide cover.
In one exemplary embodiment it is provided that the protection against torsion for the base jaws is provided on the sides opposite the drive for the base jaws. In this way both assembly and maintenance are made easier. The cover having the feather key is advantageously screwed to the housing and sealed in respect to the housing. By means of the screwed attachment it is possible to compensate for tolerances regarding the position of the grooves in the base jaws and the housing.
Because, in accordance with the present invention, the chamber of the housing with the spline hook gear is fluidically connected with the side of the cylinder chamber facing away from the spline hook gear, no underpressure is generated when the base jaws are extended or the base jaws are retracted into the housing. Underpressure would have the serious disadvantage that gases or liquids, for example rinsing liquid, could be aspirated through the gap between the base jaws and the housing, because of which the lubricant film on the base jaws could be destroyed. Furthermore, dirt would be carried in by these liquids. The connection of this spline hook gear chamber with the chamber which is under pressure when the base jaws are extended has the considerable advantage that the spline hook gear chamber is always under pressure and therefore no medium can enter, at most fluids could run out in case of leaks.
The base jaws can preferably be equipped with gripper jaws on the front. These are flanged to them, for example by means of screws, wherein they can be centered in addition.
The base jaws can preferably be retracted completely over their entire length into the housing. In the process they are completely surrounded over their entire length by the housing, so that only their front ends, on which the gripper jaws are fastened, are accessible. This has the considerable advantage that in the course of retraction into the housing the base jaws are both cleaned and also freshly lubricated.
In one exemplary embodiment the base jaws advantageously have receptacle openings for elements for position determination. The open position and the closed position of the gripper device can be determined by means of position detection elements, and the controls can be correspondingly triggered.
The present invention is not limited to two-finger parallel grippers, for example, but also includes grippers with several base and gripper jaws, for example three-finger centric grippers.
Further advantages, features and details of the present invention ensue from the following description, wherein two particularly preferred exemplary embodiments are described in detail, making reference to the drawings. The features represented in the drawings and mentioned in the claims and specification can be important for the present invention here either individually by themselves or in any arbitrary combination. The drawings show in: